The present invention relates to methods of joining a length of material to a continuously moving substrate, and more particularly to methods of joining an elastic material to a continuously moving, partially elastic substrate.
There are, today, an increasing number of products incorporating some type of elastic material to provide stretch to the products. Examples of these products incorporating elastic material include general wearing apparel, athletic apparel, and specialized apparel, such as surgical gowns, hospital gowns, and other medically-related apparel.
Other examples of different types of product include vehicle protective covers, camping-related materials such as tents for example, or the like.
Still other examples include disposable absorbent articles, such as baby diapers, children's training pants, adult incontinence products, feminine care products, or the like.
One of the intended purposes of incorporating elastic materials into these products is to keep the products secure or snug in their proper positions. For example, certain designs of general wearing apparel may require a tight fit so as to have a uniquely fashionable look. Athletic apparel needs to be maintained in place during aggressive physical activity required in some sports. Surgical and hospital apparel needs to fit properly for sanitary and health purposes.
Similarly, vehicle protective covers and camping-related materials desirably should withstand the effects of high or gusty winds and other severe weather conditions. A secure fit, whether over a vehicle or a tent frame, for example, can help weather these types of outdoor conditions.
In the area of disposable absorbent articles, a proper fit, both before and after an accident or insult, is important in preventing body waste material from leaking out of the product onto the wearer.
One problem associated with incorporating an elastic material into a product is the elastic material's potentially premature contracting during the manufacturing process. Any premature gathering of the product can cause subsequent processing steps to be off-line or unregistered, thereby resulting in material waste and increased costs in manufacture. One specific example of this is a training pant intended to be worn during the potty-training stage of young children. One style of training pant has elastic side panels that fit against the hips of the child, and discrete front and back elastic waist strips adjacent the waist opening. The waist strips are applied during the manufacturing process, and generally at a different point or time in the process from the elastic side panels. The individual training pants are folded and bonded along portions of side edges to form a waist opening and a pair of leg openings. If, for example, the elastic waist strips prematurely gather, the subsequent folding and bonding steps will not be properly performed, thereby resulting in irregular products that must be culled and disposed of.
Another problem associated with incorporating an elastic material into a product is the difficulty of properly maintaining a desired elasticity in the product during both the joining of the elastic material and subsequent handling steps. If the desired elasticity cannot be maintained, the product may not fit properly, and ultimately result in unsatisfactory performance.
A further problem exists when incorporating an elastic material into a partially elastic product, and particularly during the manufacturing process when the extensible direction of the elastic material is different from the direction of run of a continuous, partially elastic substrate, from which multiple individual products will be made. This problem is complicated when the partially elastic substrate is extensible in the same direction as the elastic material and it is desired that the joining of the elastic material should not substantially inhibit the desired elasticity of the partially elastic substrate. For example, the continuously running length of partially elastic substrate, from which some type of apparel is to be made, can have elastic portions that extend in a direction transverse to the direction the substrate is being run. A problem arises here when an elastic material, such as an elastic band for example, is to be joined to the partially elastic substrate such that the direction of extension of the elastic band also is transverse to the direction the partially elastic substrate is being run.
Yet another problem is the accurate joining of an elastic material in today's high speed manufacturing environment. Some products are manufactured at speeds of about 200-800 products per minute. Since the materials that form the product are provided at relatively high speeds, problems in material handling must be avoided if the manufacturing process is to be fast, continuous, and economical. Otherwise, there will be unacceptable and costly downtime in the manufacturing process to correct these problems.
In view of the above, there is a need today for a process for joining an elastic material to a continuously moving, partially elastic substrate.
In one form of the present invention there is provided a method of joining a plurality of elastic bands to a continuously moving, partially elastic substrate comprising the steps of (1) continuously moving in a first direction a substrate including a plurality of non-elastic segments and a plurality of elastic segments that are extensible in a second direction different from the first direction, (2) providing a supply of an elastic band and tensioning the elastic band, (3) temporarily inhibiting portions of the elastic band, (4) cutting the elastic band into individual elastic bands so that each individual elastic band includes at least one temporarily inhibited portion and at least one elastic portion, (5) sequentially orienting each individual elastic band so that it is extensible in substantially the same direction as the elastic segments of the continuously moving substrate, (6) positioning each individual elastic band over the continuously moving substrate so that each elastic portion of the band is over one of the elastic segments of the substrate, and each temporarily inhibited portion of the band is over one of the non-elastic segments of the substrate, and (7) joining each individual elastic band to the continuously moving substrate.
In another form of the present invention there is provided a method of joining a plurality of elastic bands to a continuously moving, partially elastic composite structure comprising the steps of (1) continuously moving in a first direction a composite structure including a continuous topsheet, a continuous backsheet, a plurality of spaced apart absorbent structures between the continuous topsheet and continuous backsheet, and a plurality of spaced apart elastic side members on opposite sides of the continuous backsheet and being extensible in a second direction different from the first direction, (2) providing a supply of an elastic band and tensioning the elastic band, (3) temporarily inhibiting portions of the elastic band, (4) cutting the elastic band into individual elastic bands so that each individual elastic band includes a pair of elastic portions and a temporarily inhibited portion therebetween, (5) sequentially orienting each individual elastic band so that it is extensible in substantially the same direction as the elastic side members, (6) positioning each individual elastic band over the continuously moving composite structure so that the temporarily inhibited portion of the band is over the backsheet, and a pair of elastic portions are over a respective pair of opposite spaced apart elastic side members, and (7) joining each individual elastic band to the continuously moving composite structure.